This invention relates to the manufacture of food products, and in particular to a new and improved cooling tunnel for use in high speed production of food products. The specific embodiment disclosed is used for the cooling of baked tortillas and the like prior to subsequent operations such as stacking or cutting and frying.
Cooling tunnels are widely used today and typically include a housing with a conveyor therein for moving the product through the tunnel. Blowers or fans provide for moving air and other gases, such as carbon dioxide, over the product, with the conveyor preferably being aperatured to permit flow of the gases through the conveyor. The carbon dioxide may be introduced by spraying liquid carbon dioxide into the cooling space to provide chilled air and carbon dioxide gas for cooling. Movement of the gases over the food product is enhanced by exhaust ducts and fans.
Problems are encountered in the operation of such cooling tunnels, particularly with high capacity tunnels providing for high speed movement of the product through the tunnel and for high velocity of cooling gas flow. In such tunnels, the fans within the tunnel are used to produce a storm of air or turbulence to achieve thorough mixing of the injected carbon dioxide and the incoming air. Fans are used in the exhaust ducts for drawing the gas mix past the product and out of the tunnel. Some food products, such as tortillas, have a relatively large surface area while being quite thin, and the high velocity movement in the tunnel tends to lift and move the product over the conveyor. This results in undesired overlapping of products, creasing or folding of product and other forms of damage to the product, such as product being blown upward and cut apart by the blades of the fans.
It is an object of the present invention to provide a new and improved cooling tunnel which can be operated at high product rate and high cooling rate without the risk of damage to the product being cooled.
It is a particular object of the invention to provide such a cooling tunnel incorporating closed loop flexible hold down devices which will engage and restrain the food product as it enters the cooling tunnel and maintain the product in position on the conveyor until it leaves the cooling tunnel. A specific object is to provide such a tunnel utilizing closed loop flexible and slack hold down chains which can be positioned on the food product which in turn is positioned on the conveyor, with the chains moving with product and the conveyor from the entrance to the exit of the tunnel.
These and other objects, advantages, features, and results more fully appear in the course of the following description.